Nozzle for desurfacing metal



July 11, 1944. A. P. scHl-:LLER 2,353,318

NOZZLE FOR DESURFACING METAL Filed March 8, 1940 ATTORNEY Patented July 11, 1944 NOZZLE FOR DESURFACING METAL Arthur P. Scheller, Irvington, N. J., assigner to The Linde Air Products Company, a corporation of Ohio Application March. `8, 1940, Serial No. 322,965

(Cl. 15S-27.4)

sages. The latter are supplied with a combusti- 6 Claims.

This invention relates to an apparatus for desurfacing metal bodies, and more particularly to blowpipe nozzles, and the making thereof, which are especially useful in connection with surface metal removal by effecting a progressive thermochemical reaction of such metal with an oxidizing medium.

When an oxidizing gas stream of suitable character is directed obliquely against a work surface, such as that of a ferrous metal body suitably heated to an ignition temperature, and moved along said surface, a thermochemical reaction takes place between the oxygen and the ferrous surface metal, which leaves a bright, clean area. Part of the metal removed is oxidized to form a molten slag and part of the metal is melted by the heat of the reaction. A Wave of such mixed molten metal and slag is advanced by the force of the oxidizing fluid stream over the surface metal to be removed and assists in properly heating the surface portions of the base metal immediately prior to the actual desurfacing reaction. In desurfacing a relatively wide area, it has been customary to arrange two or more blowpipe nozzles to direct oxidizing fluid jets against the work surface. Such nozzles had circular oxygen orifices and produced substantially cylindrical oxygen jets flowing with a relatively low velocity, i. e., a velocity below about 1000 feet per second. Each such jet makes an individual groove in the work surface, so that a ridge is formed between adjacent grooves by the desurfacing operation.

Such ridge formation conceals and often contains defective metal which it was intended to eliminate by the desurfacing operation. Also surface defects intended to be removed by the desurfacing, while removed completely within the channels, are only partially or removed not at all in the region of the ridges. Subsequent working or rolling of the metal body causes the ble mixture oi' fuel gas, such as acetylene, and combustion supporting gas, such as air or oxygen. Thus, in operation, a series of heating flame jets issue from such preheat gas passages. The oxidizing fluid supplied to the central passage is preferably oxygen. The oxygen passages of Ithrough such nozzles is relatively limited. With nozzles having cylindrical orifices it has not been possible to remove surface metal efficiently so as to produce smooth channels with gas velocities substantially exceeding the acoustic velocity. The use of a row of such nozzles for desurfacing a wide area produces transversely concave grooves divided by objectionable ridges, as pointed out above.

Therefore, the main objects of this invention are to provide: an improved apparatus for removing surface metal from ferrous metal bodies adapted to overcome the disadvantages and objectionable features of the prior art in the matter of ridge formation; a nozzle for efficiently removing surface metal with oxygen streams flowing with velocities exceeding the acoustic velocity; an improved blowpipe nozzle for use in desurfacing, that is simple and economical in its parts and very eiiicient and effective-in operation; a novel method of altering a conventional blowpipe nozzle to obtain improved results in desurfacing; and a desurfacing blowpipe nozzle capable of efficient operation with a relatively wide range of gas flow rates.

The above and other objects and novel features of this invention will become apparent from the following description taken with the accompanying drawing in which:

Fig. l is a fragmentary perspective View of a' desurfacing unit employing a row of nozzles embodying the principles of this invention, in operation;

Fig. 2 is a view in front end elevation on an enlarged scale of a blowpipe nozzle constructed according to the invention;

Fig. 3 is a view in longitudinal section of the nozzle taken on a line corresponding to line 3-1' of Fig. 2;

Fig. 4 is a similar view in longitudinal section of a modified form of nozzle according to the invention;

Fig. 5 is a fragmentary perspective view showing the location of the inserts in the nozzle, the end portion of the nozzle being indicated by broken lines; and

Fig. 6 is a fragmentary View of a longitudinal section taken on the line 6-6 of Fig. 3 showing an insert and the lateral slots.

In general the improved blowpipe nozzle according to the invention is particularly adapted for a multiple nozzle desurfacing head or unit as illustrated in Fig. 1. Each nozzle has the outlet portion of its desurfacing oxygen rpassage shaped so that it changes smoothly from a circular passage to a slot-like exit orifice having substantially flat top and bottom edges and the passages are so shaped as to produce a uniform velocity distribution. Such nozzles make individual grooves that are substantially flat, and when suitably spaced in a. row in a desurfacing head, the edges of the adjacent oxygen streams merge to produce a substantially continuous wide desuri'acing stream thereby to eliminate or greatly reduce the objectionable ridges and remove all the defective surface metal.

'Ihe cross-sectional area of the slot-like exit orifice, for best results, may be the same as, or slightly less than, the Icross-sectional area of the circular passage adjacent to the altered portion. The cross-sectional area of the altered portion is either constant or uniformly reduced, so that the passage is streamlined and has no abrupt changes in its cross-sectional area..

According to this invention, the nozzle N may be produced from a blank of a conventional blowpipe nozzle having an axial oxygen passage O by forming a concentric series of suitably spaced longitudinal preheat passages P, in the nozzle blank and modifying the orifice end portion of the passage O. Diametrically opposed divergent slots or grooves I0, I are then machined in the body of the nozzle in the walls of the oxygen passage O. The slots I Ii are of greatest depth at the end face II of the nozzle and extend inwardly to a point I2 where their depth tapers to zero. The walls of the slots IIJ are preferably in the shape of sections of oblique cylinders the bases of which lie in the plane of the face I I and the axes of which are inclined at equal angles relatively to the axis of the passage O and intersect at a point on said axis within the nozzle.

'I'he nozzle Iblank employed for the form of nozzle illustrated in Figs. 2, 3, 5, and 6 has an oxygen passage O comprising a cylindrical bore portion I3 extending back from the face II, a constricted inlet portion Il and a tapered portion I joining the inlet I4 and the bore I3. The inlet Il is of a diameter to pass the desired volume of oxygen when the oxygen is supplied at a suitable head pressure through a supply passage S in a blowpipe head indicated at H. The blowpipe head H is preferably of a. type suitable for receiving a closely spaced row of desurfacing blowlpipes and has nozzle receiving openings of the customary construction adapted to receive and hold the nozzles N, the nozzles N being retained by ring nuts R acting against a shoulder K adjacent the inlet end of the nozzles. The preheating gas passages P of the nozzle are supplied with mixed combustible gas by a channel C in the head H with which they communicate.

To form, with the slots I 0, the delivery orince of the nozzle according to the invention, a pair of tapered inserts It, Il are then secured within the bore Il adjacent the face II opposite elch other. The inserts II preferably comprise oblique sections of a right cylinder the cylindrical surface portion of which coincides with and is in contact with the bore Il, the base of which insert coincides with the discharge end face II, and the oblique planes of which are equally inclined relatively to the axis of the bore Il and intersect along a line which intersects said axis perpendicularly at an external point in front of the face II. The inserts I6 taper inwardly to rpoints I1 on elements of. the bore I3 spaced at from the elements of the bore on which are located points I2.

The inserts I6, I6 are disposed so that their straight base edges are alined with the slots Il and may be secured by holding them in place by any suitable means, such as clamps, while small angularly related holes are bored through the tubular body of the nozzle N and into the inserts I6. These holes are then filled with pins Il and the inserts preferably sweated in place with silver solder flowed into the joints.

While the nozzle blank employed is preferably one that has the preheat passages P originally symmetrically spaced on each side of the slotted outlet orifice it will be evident that a nozzle blank having preheat passages P formed therein completely symmetrically about the cylindrical passage I3 could also be employed by first plugging with silver solder those preheat passages which would interfere with the slots I 0 and if necessary redrilling one or more preheat passages.

In the form of nozzle illustrated in FM. 3 the oxygen flow is metered by the inlet restriction I4. The stream of oxygen then expands in the portion I5 at a rate sufllcient to effect a reduction of velocity. In the portion I3 the stream becomes substantially non-turbulent and in the portion of the passage between the faces of the inserts I6 and beyond the points I 1, the flow is changed smoothly from a cylindrical flow to a sectionally oval flow, the stream becoming ribbon-like at the exit face II, that is, like a ribbon of substantial thickness having non-parallel edges since the stream continues to expand in width at a substantial rate as well as slightly in thickness after leaving the nozzle. In the portion of the passage from points I1 to points I2 the cross-sectional area gradually decreases and the flow velocity increases. From the points I2 to the end face II, the upper and lower walls of the passage continue to converge but the side walls of the passage which are now formed by the slots I0, diverge. The rate of such divergence is so chosen that the cross-sectional area o! the passage in the plane of the face II is substantially equal to the cross-sectional area of the passage in the region of the points I2. With such relation between the upper and lower and side walls of the passage, it is found that the ribbonlike stream of oxygen produced by the nozzle flows with a substantially uniform velocity throughout the entire width of the stream. It

is important that the velocity be uniform in order to produce substantially i'lat desurfacing cuts. Furthermore the stream expands very little in the vertical direction but will expand edgewise or laterally yjust the right amount to merge properly with adjacent streams when several such nozzles are mounted in a row and properly spaced as in Fig. 1.

In the modified form of nozzle illustrated in Fig. 4 yand which has an end viewappearance similar to Fig. 2, the cylindrical bore il is of substantially constant diameter to the inlet end of the nozzle N and the slots I taper topoints I2 which are substantially in the same transverse right plane as the points i1 of the inserts I8. The oxygen passage in this form of nozzle is substantially of constant cross-sectional area throughout. The control of the quantity of oxygen flowing may be effected by a metering passage in the blowpipe head or .by controlling the flow rate to the nozzle. The divergence of the side walls of the passage from the points i2 to the face il is preferably such as to balance the convergence of the top and bottom walls from the points i1 to the face il so that the crosssectional area of the passage in the plane of the points I2 and il is substantially the same as the area of the slotted end orifice. If desired, the nozzle N' may also be provided With an inlet restriction similar to passage il.

The resulting arrangement is preferably such that there is provided a streamlined oxidizing fluid flow passage at least the end portion of which is of substantially constant cross-sectional area and has a cross-sectional shape that gradually changes from circular to oblong shape at the discharge face II of the nozzle. The long sides of the oblong shape are straight and substantially parallel, and the short sides thereof are preferably curved.

The above-described method of making the nozzles is simple and relatively inexpensive because the parts are readily available and there results a precision instrument. However, various changes may be made in the detailed method of construction disclosed therein without departing from the principles of the invention provided that substantially the same shape of oxygen passage results. For example, the nozzle may be formed from a single piece of metal.

The blowpipe .nozzles N or N' are assembled in a desurfacing apparatus indicated fragmentarily at A and comprising a head plate I9 through which the individual nozzles pass and are supported in a row for longitudinal and rotational adjustment. The nozzles are preferably positioned with the long sides of the orifices in parallel relation to the surface of the work W which may be the top surface of a steel billet, inot or slab. The axes of the nozzles are held at an acute angle to the surface 20 in order to impinge the oxidizing streams 2i along and obliquely against the surface. The slot-like exit orifices of the passages O or O are arranged in transverse alinement for normal operation and the nozzles are spaced so that the oxygen streams 2i combine or merge smoothly into one wide substantially continuous fiat sheet at the zone of reaction indicated at Z, thus, advancing the molten metal and slag in a uniform wave 22 and leaving a clean, flat, new surface 23 on the work.

The desurfacing apparatus A may be normally stationary while the work W is moved relatively thereto toward the plate I9, but if desired, th'e work may be stationary while the apparatus A is advanced for the desurfacing operation. The lower surface of the plate I9 preferably is guided on the surface 23 to maintain the nozzle orifices at a constant elevation from the work surface. The preheating flame jets issuing from the preheat passages P operate in the usual way to assist in maintaining the thermochemical reaction of the oxygen with the ferrous surface metal under-- going treatment.

The use of -blowpipe nozzles of this invention in a multiple nozzle desurfacing head results in the removal of a uniform layer of metal from the work surface. leaving a surface that is free oi.' ridge formation. Thus, all surface defects and flaws which are no deeper than thedepth of the desurfacing operation are removed. The desurfaced area may be of uniform or uniformly varied depth, as desired, and more of the defective surface metal is removed than is possible with conventional nozzles.

With conventional round nozzles it is usually necessary to remove metal to a greater depth at the center of the channels produced than the depth of the defects in order to remove most ofthe defective surface metal. When a uniform layer of metal is removed the depth of removal need not be as great in order to remove all defects and therefore the employment of nozzles according to this invention will provide greater over-all economy.

Good results have been obtained with a nozzie embodying the principles of this invention and having an oxygen passage provided with an inlet restriction of about .2.77 inch diameter, a maximum cross-sectional area of about .135 square inch and a cross-sectional area at the end orifice of about 0.067 square inch, the width of the slot being about 1/8 inch. Such a nozzle will produce an oxygen stream effecting efflcient surface metal removal with a relatively wide range of gas flow rates between about 1500 cubic feet per hour to 3500 cubic feet per hour and stream velocities of from about 600 feet per second to about 2000 feet per second or considerably in excess of the acoustic velocity. These velocities are on the basis of normal temperature and pressure conditions as the conditions in the stream are difficult to measure.

It will be noted that the narrow sides of the oxygen passage of the nozzle of this invention diverge or are outwardly. The angle of divergence preferably should be such that the oxygen streams where they strike the work surface merge to form a sheet of oxygen of substantially uniform depth transversely of the surface. If there is too much overlapping of the oxygen streams there will be a gouging effect so that'instead of removing undesirable ridges` there may be produced grooves which are also undesirable.

With the specific example of nozzle disclosed above and having the orifice side walls diverging to include an angle of about 24, the center-tocenter spacing of the nozzle orifices in the head A should be about 11% inches. It has been found that substantially flat surfaces are produced when the spacing is between 111g inches to about 11/4 inches. It has also been found that a divergence of the side walls of the outlet passage in conjunction with a convergence of the top and bottom walls is essential to produce auniform distribution of velocity of flow of the stream throughout the width of the ribbon-like stream. If the divergence is too small or too great, the velocity distribution becomes uneven and a nonuniform depth of cut will result.

The oxygen streams from the desurfacing nozzles are directed downwardly and obliquely onto the Work surface in the general direction of advance and the reaction puddle formed by each jet or stream is proportional to the size and shape of the cross-sectional area of the surface metal removed by the desurfacing operation. The

length of the individual puddles or of the combined puddle, measured in the direction of advance, must be appreciable, to maintain the stability of the desurfacing operation. That is to say, if the puddle or wave of molten metal and slag is too short the desurfacing operation may be lost or be deflected by irregularities of the original surface. The length of puddle is dependent on the thickness of the stream and therefore the oxygen stream must be of sufficient thickness to maintain a. puddle of sufficient length. The vertical or shortest dimension of the oxygen stream also must not be too narrow'or the stream will tend to deform and become feathery. This is probably due to the friction effects of the side walls of the orifice and turbulence caused by the surrounding air.

It has also been discovered that for the purpose of making a substantially nat cut, it is essential that the bottom surface only of the stream shall be iiat. Therefore, the lower edge of the orifice should be straight. The center portion of the upper edge could be higher in order that the center of the jet be thicker to obtain greater stability of reaction but the center portion of the stream should not be thinner than the lateral portions.

Desurfacing heads having a row of nozzles constructed as specifically disclosed herein have been operated to emciently remove a layer of surface metal to a uniform depth from steel billets at rolling temperatures with speeds of advance ranging up to 450 feet per minute. It will be seen that nozzles constructed and arranged according to the present invention provide new and highly advantageous results by not only eliminating the production of ridges in desurfacing but permitting high speeds of surface removal, smaller loss of surface metal, stability of operation, and excellent economy.

Other uses for the nozzle disclosed herein may be found and it will be apparent that modifications of the nozzle may be made and in the process of making and using the nozzle and that certain features can be used independently of others without departing from the spirit and scope ofthe invention as set forth in the claims. For example, the upper insert might be omitted altogether or there may be substituted for the upper insert i6 an insert which does not have a flat oblique surface but one that is higher in its center portions. Where oxygen is named in the claims it should be understood to include not only substantially pure oxygen Ibut also oxygen containing mixtures.

I claim:

l. A blowpipe nozzle having an axial oxygen passage therethrough, said passage having an inlet portion, a laterally wide discharge orice and an intermediate portion of slightly larger cross-sectional area tha'n said discharge orice, the upper and lower Walls of said passage gradually converging from said intermediate portion to said discharge oriiice and the lateral side walls of said passage diverging from the width of said intermediate portion to said discharge oririce, the divergence of said side walls beginning at a transverse plane between the discharge orifice and the transverse plane Where the upper and lower walls begin to converge, and the degree of divergence of said side walls being such that the cross-sectional area of the discharge orice is substantially equal to the cross-sectional area of the passage at the plane where the divergence of the side walls begins.

2. A blowpipe nozzle having an axial oxygen passage therethrough, said passage having an inlet portion, a laterally wide discharge orifice. and an intermediate portion therebetween having a larger cross-sectional area than that of either said inlet portion or said discharge portion, upper and lower walls converging gradually from the height of said intermediate portion to the height of said discharge orifice, and side walls diverging from the width of said intermediate portion to the width of said discharge orifice, the divergence of said side walls beginning at a transverse plane between said discharge orifice and the beginning of the convergence of the top and bottom Walls, the degree of divergence of the side walls being such that the cross-sectional area of the discharge oriiice is substantially equal to the cross-sectional area of the passage at the plane where the divergence of the side walls begins.

3. A blowpipe nozzle comprising in combination a body having a cylindrical bore extending inwardly from the discharge end o! the nozzle: a pair of inserts secured to said body at opposite sides of said bore, said inserts comprising oblique cylindrical wedges the cylindrical surfaces of which coincide with said bore, the bases of which coincide with said discharge end of said nozzle, and the planes of the oblique inner surfaces of which are equally inclined relatively to the axis of said bore and intersect said axis along a line perpendicular thereto externally of said discharge end; and a pair of slots in the walls of said bore between said inserts, said slots being opposite each other and extending inwardly from the discharge end of said nozzle, said slots being deepest at said discharge end and of decreasing depth inwardly and forming diverging side walls cooperating with the converging upper and lower walls formed by said inserts to provide a fluid discharge passage which smoothly changesfrom circular shape internally of the nozzle to oblong shape at the discharge orifice en d, the degree of divergence of said side walls being so correlated with the degree of convergence of said upper and lower walls that the cross-sectional area of said discharge orifice is substantially equal to the cross-sectional area of the passage in the region Where the divergence of the side walls begins.

4. A blowpipe nozzle having an oxidizing gas passage therein, said nozzle comprising a metal body having a right cylindrical bore therein extending axially a substantial distance inward from the outlet end of the nozzle, a pair of inclined slots in said body at opposite sides of said bore forming divergent side wall portions of said passage, and a pair of tapered inserts secured to said body between said slots and against the opposite sides of said bore and forming convergent upper and lower walls of said passage, said slots and said inserts cooperating to form a laterally wide discharge orii'lce, the degree of divergence of said side walls being so correlated with the degree of convergence of said upper and lower walls that the cross-sectional area of said discharge orifice is substantially equal to the cross-sectional area of the passage in the region where the divergence 0f the side Walls begins.

5. A blowpipe nozzle having a central oxygen passage surrounded by a series of preheat passages having outlet orices disposed on a circular line of centers which is concentric with the longitudinal axis of said central oxygen passage, the side walls of said central oxygen passage diverging and being formed by opposed slots in opposite sides of said passage that increase in depth from their inner ends to a maximum depth at the discharge end of said central passage, and inserts secured against and shaped to rit the top and bottom walls of said passage and having inclined inner surfaces to form convergent upper and lower walls, said slots and said inserts cooperating to form-a laterally wide discharge orice, the degree of divergence of said side walls being so correlated with the 4degree of convergence of said upper and lower walls that the cross-sectional area. of said discharge orice is substantially equal to the cross-sectional area of the passage in the region where the divergence of the side Walls begins.

6. A blowpipe nozzle having an axial oxygen passage therethrough, said passage having an inlet portion, a laterally wide discharge orifice,

and an intermediate portion having at least as large a cross-sectional area as said discharge orice, the upper and lower walls of said passage gradually converging from said intermediate portion to said discharge orifice and the side Walls of said passage diverging from the width of said intermediate portion to said discharge orifice, the divergence of said side Walls beginning at a transverse plane nearer the vdischarge orice than the transverse plane Where the upper and lower Walls begin to converge, the degree of divergence of said side walls being so correlated with the degree of convergence of said upper and lower walls that the cross-sectional area of said discharge orifice is substantially equal to the cross-sectional area of the passage at the plane Where the divergence of the side walls begins.

ARTHUR P. SCHELLER. 

